The present invention relates to a water heater control system. More particularly, the present invention relates to a control system for a hot water heater, in which the water within the heater is heated only upon demand.
Conventional hot water heating systems maintain a predetermined temperature of the water in storage. The heat energy which is lost through the insulation of a typical water heater storage tank on a daily basis can amount to as much as 3400 BTU of energy per 10 gallons of storage water at a temperature of 140.degree. F. This means that a 60 gallon water tank will use over 20,000 BTU's per day to maintain the contents at a temperature of 140.degree. F., due to energy losses through the insulation of the tank.
Previous hot water heater control systems are described, for example, in the following U.S. Pat. Nos.: 2,480,302 to Pankow; 2,852,018 to Williams; 3,484,580 to Morgan; 4,058,702 to Jerles; and 4,166,944 to Scott. Such previous systems are primarily concerned with maintaining water in the system at a specific temperature or temperature range over an extended period of time, even though there may be no demand for hot water during a relatively long time period.
By the present invention, there is provided a water heater control system which eliminates essentially all of the storage heat losses during the periods when hot water is not needed. Such an energy saving is achieved by heating only that water which is to be utilized in the immediate future, and by not allowing the heating to continue after such hot water is consumed. Thus the water in the water heater storage unit is maintained in a substantially cold condition except on the occasions when hot water is actually needed. The water heater control system of the present invention can provide substantial savings when employed with the hot water heater utilized by a typical family in the home.
The present invention is particularly useful in solar hot water heating applications. A consumer who owns a solar hot water heating system is operating the system at reduced efficiency when the water must be maintained at a constant temperature by the use of supplemental electric or gas heat. Many consumers, faced with such reduced efficiency, have inactiviated their hot water circuit breaker. In inclement weather, however, when the solar contribution is not sufficient, the consumer must turn the circuit breaker on, then guess how long he must wait before the water is hot enough. Such a practice is not only inconvenient but also increases the loss of heat, particularly if the time from heat up to use of the water is excessive. Also, the circuit breaker must be turned off again when hot water is no longer required.
The present invention also provides for significant savings in nonsolar applications. As an example, hot water heaters are typically set at a temperature in the range of 150.degree.-180.degree. F. for dishwasher requirements. Such a practice causes unnecessary heat losses when only warm water is required, such as for a bath or for doing the laundry, since the temperature differential between the hot water and the ambient temperature is unnecessarily high.
The water heater control system of the present invention includes: a relay box and a pair of thermostatically controlled switches which are usually mounted on the water heater; and a remote control unit which can be located in the kitchen or other convenient location in the home. The remote control unit provides both an indication of the present condition of the water temperature in the water heater, and also means for initiating the heating cycle in order to heat the temperature in the heater to either of two selected temperatures. Operation of the remote control unit when hot water is desired will energize certain relays in the relay box, thus providing heat to the water heater upon selective demand to heat the water to either of the two preselected temperatures. The present invention provides for heating the water to a selected temperature, at which time the heating unit is de-energized so that heating of water in the heater will not occur again until the water temperature drops below a selected temperature and the operator initiates operation of the system for the heating cycle to be repeated.